This research proposal describes experiments aimed at determining the molecular basis for mutation and polymorphism at the waxy (Wx) locus of maize. Waxy has been chosen as the focus of this study because it is, at the genetic level, the best characterized higher plant gene; there are over 40 mutant alleles available for analysis. In addition, the Wx gene has been cloned and characterized and all Wx gene products can be easily assayed. Four mutant alleles and many germinal derivatives resultnig from insertion and excision of the transposable elements Activator (Ac) or Dissociation (Ds) will be characterized. Each allele has a unique unstable waxy phenotype; one goal of this proposal is to describe the molecular basis for these phenotypic differences. Experiments are proposed to understand why (1) wx-ml(Ds) can produce new alleles with a gradient of Wx expression, (2) wxB3(Ac) displays only very late somatic reversion, (3) the Ac element in a derivative of wx-m7(Ac) is inactive, (4) wx-m5(Ds) appears to flip-flop from one unstable form to another and (5) an active Ac element may suppress gene expression. Insertions, deletions and rearrangements, found to be the lesions responsible for stable Wx muatations, will also be analyzed in detail. In addition, 2 insertion polymorphisms flanking the Wx gene in certain inbred lines will be characterized. For all proposed research, standard techniques of recombinant DNA and DNA biochemistry will be employed. The project is expected to contribute to an understanding of the elements responsible for restructuring the genomes of higher plants.